[post_ad]Default Routing used only in a stub network which has only one exit interface in this type of Routing administrator dose not has knowledge of the destination but it must know the next hope address . it is mainly used that type of routing which has slower link. It has very less security.
Configuration of default Routing
Syntax- Router(config)# ip route <destination address> <destination mask> <next hope address>
RouterA(config)# ip route 0.0.0.0 0.0.0.0 172.16.2.1
RouterB(config)# ip route 0.0.0.0 0.0.0.0 172.16.2.2